v4l2-ctl: update page (#10464)

* v4l2-ctl: update page

Changed one of the video device filepaths to relative and added a new entry for setting a value.

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/linux/v4l2-ctl.md

@@ -29,4 +29,8 @@
 
 - List all video device's controls and their values:
 
-`v4l2-ctl --list-ctrls --device {{/path/to/video_device}}`
+`v4l2-ctl --list-ctrls --device {{path/to/video_device}}`
+
+- Set the value of a video device control:
+
+`v4l2-ctl --device {{path/to/video_device}} --set-ctrl={{control_name}}={{value}}`